Known dry-cleaning processes consist of wash, rinse, and drying cycles. Garments are loaded into a basket in a cleaning drum and immersed in a dry-cleaning fluid or solvent, which is pumped into the cleaning drum from a base tank. Conventional dry-cleaning fluids include perchloroethylene (PCE), petroleum-based or Stoddard solvents, CFC-113, and 1,1,1-trichloroethane, all of which are generally aided by a detergent. The solvent is used to dissolve soluble contaminants, such as oils, and to entrain and wash away insoluble contaminants, such as dirt.
The use of these conventional solvents, however, poses a number of health and safety risks as well as being environmentally hazardous. For example, halogenated solvents are known to be environmentally unfriendly, and at least one of these solvents, PCE, is a suspected carcinogen. Known petroleum-based solvents are flammable and can contribute to the production of smog. Accordingly, dry-cleaning systems which utilize dense phase fluids, such as liquid carbon dioxide, as a cleaning medium have been developed. An apparatus and method for employing liquid carbon dioxide as the dry-cleaning solvent is disclosed in U.S. Pat. No. 5,467,492, entitled "Dry-Cleaning Garments Using Liquid Carbon Dioxide Under Agitation As Cleaning Medium". A similar dry-cleaning apparatus is also disclosed in U.S. Pat. No. 5,651,276.
These systems pose a number of other problems, particularly in relation to the high operating pressures necessary for maintaining the gas in a liquid state. Specifically, the cleaning vessel in a liquid carbon dioxide system operates at between 500-850 psi under ambient temperature conditions. In addition to the cleaning vessel, the dry-cleaning apparatus has a number of other vessels or chambers associated with the regular operation and maintenance of the system which are regularly exposed to elevated pressures. Because of the high operating pressures, the doors, access panels, hatches and the like associated with the various pressure vessels in the system have relatively bulky heavy-walled constructions. A number of these pressure vessels or chambers contain filters and cleanout areas, such as for example the lint filter, which should be accessed on a regular basis for routine cleaning or maintenance, sometimes as frequently as after the completion of each laundry load. In order to encourage regular cleaning of these filters and clean-out areas, they should be readily accessible to an operator. While the size and weight of the main door on the cleaning vessel requires the provision of an automated opening and closing mechanism, the smaller doors such as the lint filter access door are generally intended to be operated manually. However, because of the bulky heavy-walled construction of these doors, they can be cumbersome to handle and can require a significant amount of physical strength to operate.
These difficulties can make it inconvenient for an operator to open such pressure vessels or chambers and, in the case of the lint filter, can discourage the operator from checking and cleaning the lint filter as frequently as is needed to ensure optimal operation of the dry cleaning system. For example, doors which are used on smaller pressure vessels, such as the lint filter in a liquid carbon dioxide dry cleaning system, commonly are designed for threaded closing engagement. In particular, the door is moved between open and closed positions, by threading the door into and out of engagement with a complementary threaded opening in the pressure vessel. However, the weight of the door can make it difficult to rotate, often necessitating the use of a separate tool. As will be appreciated, using a separate tool to open the door can be time consuming and awkward resulting in misapplication of the tool. Moreover, the separate tool can easily become misplaced or lost. In the context of the access door to the lint filter, this can make checking the filter on a regular basis even more inconvenient for an operator. Additionally, once the door is removed from the filter housing in order to gain access to the lint filter, the door itself must be manually set aside so that the operator can check and, if necessary, clean the lint filter.
Difficulties also can arise when closing the filter access door. Specifically, in order to ensure that the lint filter housing is tightly sealed, the door must be aligned to properly engage the complementary threads in the opening in the filter housing. Because of the weight of the door, this can be a quite cumbersome and frequently time-consuming operation. If the threads are not properly engaged, of course, it can result in a potentially hazardous leak of high pressure carbon dioxide.